Air-cushion maritime craft

ABSTRACT

A craft in which the bottom between the board keels is provided with steps located at a definite distance one from another and forming a stable air-cushion under the bottom of the craft.

I United States Patent [15] 3,659,542

Petrov et al. May 2, 1972 54] AIR-CUSHION MARITIME CRAFT 52 us. Cl. ..114/67A [72] Inventors: Vltaly Ivanovich Petrov, ulitsa Frunze, 6a kv. 147; Alexandr Nikohevich Ivanov, Basseinaya ulitsa, 3|, kv. 29; Jury 6 Leonidovich Olenin, Moskovskoe shosse, [5 1 References Cl 20, korpus 5, kv. 5; Arnold Oskarovich UNITED STATES PATENTS Eller, V.O., 6 Llnia, 49, kv. l9; Anatoly Mimic BMW Kransnopmflovskaya iii??? 132321 lY -iiii r'a iii: ..'....'....1..'.'.:..114,67 A

ulitsa, 19, kv. 22; Abram Moiseevich Basin, ulitsa Lenina, 48, kv. 7; Vladimir Borisovich Starobinsky, ulitsa Professora Kochalova, 6, kv. 3; Efim Rafailovich Ratner, Prospekt Stachek 132 kv. 78; Oleg F edorovich Potapov, Nevsky prospekt, 23, kv. 10, all of Leningrad, U.S.S.R.

[22] Filed: Aug. 14, 1969 [21] App]. No.2 850,038

Primary Examiner-Andrew H. Farrell Att0rneyWaters, Roditi, Schwartz & Nissen [57] ABSTRACT A craft in which the bottom between the board keels is provided with steps located at a definite distance one from another and forming a stable air-cushion under the bottom of the craft.

2 Claims, 7 Drawing Figures Patented May 2, 1972 3,659,542

2 Sheets-Sheet 2 q. Q' I\ Q Q Q Q? I I I I I K) w g (\J AIR-CUSHION MARITIME CRAFT The present invention relates to shipbuilding and, more particularly, to maritime craft of the type supported on an aircushion.

The air-cushion craft made according to this invention may be most advantageously used on rivers and lakes.

Known in the art are craft in which between two keels mounted on the bottom of a cylindrical insert of a hull there is provided a chamber which is laterally limited by the keels and, at the bow and stem sides, by projections. The surface of this chamber is subdivided into approximately equal sections which are supplied with air. Mounted in the center of each such section is a probe for checking the thickness of the air cushion. This probe sends a signal to a device controlling the air supply means. Such craft are complicated in manufacture and operation.

The diagram of the above dependence at a constant value of the speed U is shown in FIG. 4. As can'be seen from this diagram, an increase of the air consumption is followed by an increase of the cushion length until the value Q reaches a certain An object of the invention is to provide a craft of a simple construction providing for a stable air cushion under the bottom thereof so that there would be no need for checking the parameters of this cushion nor for any control of the air supply.

This object is attained by providing a craft wherein the outlets of the air supply ducts are arranged on the botbom between the keels to produce an air-cushion. According to the invention, the bottom or at least the cylindrical insert of the hull is provided with steps forming an air-cushion, which steps are separated one from another by a distance determined by the ratio 1 ItV where V is the service speed of the craft in m./sec. and k is a coefficient varying within the range of 0.2 to 0.4 the outlets of the air ducts being located at least near the foremost or bow step.

The stem of I a self-propelled craft is preferably provided with at least one step located before the propellers and enveloping the bottom and a portion of each board. Such a step protects the propeller against the penetration of air by directing the air away from this propeller.

It is preferred that each step be made in the form of a plate mounted at an acute angle to the associated ship bottom thus forming a space supplied with air.

Such a construction of the steps and their location relative to the orifices of the air ducts provides for a reliable distribution of the air, which is fed into the spaces formed by the plates and the bottom, over the width of the craft. The proposed craft has a relatively simple construction providing for a stable air-cushion under the bottom.

Further objects and advantages of this invention will become more readily apparent and the invention will be better understood by reference to the following description of a specific embodiment of the invention when taken in conjunction with the accompanying drawings, in which:

FIG. I is a lateral view of the craft according to the invention;

FIG. 2 is a sectional and enlarged view taken along line II- II in FIG. 1;

FIG. 3 shows the section A of FIG. 1 on enlarged scale;

FIG. 4 is a diagram showing the dependence of the length of the air-cushion upon air consumption;

FIG. 5 is a view of the craft from the stern;

FIG. 6 is a sectional view taken along the line VIVI in FIG. 5; and

FIG. 7 is a lateral view of the craft showing the air-cushion.

The flat bottom 1 (FIGS. 1 and 2) of the air-cushion craft 2 is provided with side keels 3 which limit spreading of the air in the lateral direction. The middle keel 4 is employed for increasing the craft stability. Positioned between the keels 3 and 4 are steps 5. Each step 5 is made in the form of a plate 6 (FIG. 3) secured to the bottom 1 of the craft at an acute angle. The steps form spaces supplied with air through ducts 7. The plates 6 are secured to the bottom 1 by means of stiffeners 8.

The steps 5 are mounted at a certain distance I from each other, the selection of which depends on the objective physical laws determining the dependence of the length C of the aircushion on the air consumption Q and the craft speed U.

F eonst where F,- is the Froude number calculated for the maximum length of the air cushion,

g is gravity'acceleration.

Ifthe air-cushion is formed in the middle portion of the flat bottom, the quantity LC is approximately equal to 0.55. When the air-cushions are located not only in the middle portion of the craft but also in the stern and bow portions thereof, the cushions are afiected by the form of the ends of the craft and the quantity F,C,,,,, according to the experimental data may be within the range of 0.5 to 0.7.

It will be understood from the above that the distance I should be equal to the maximum length of the air-cushion when the craft is moving at a service speed V.

Thus the distance to be adopted between the steps can be determined by the formula The quantity F,c,,,, 0.5 0.7 corresponds to the magnitudes lying within the range 0.2 to 0.4 m./sec.

In practice the distance I should be correctedexperimentally.

At the distance between the steps equal to the maximum length of the air-cushionson the bottom of the craft moving at a service speed, the total area of the bottom covered with the air-cushions appears to be the largest. Therefore, in the case of the craft moving at a service speed, the water resistance will be minimum. If the craft speed is lower than the service speed, the bottom area covered with the air-cushions will be smaller, whereas the water resistance will be higher than in the case when the craft moves at a service speed.

The self-propelled craft equipped with'steps 5 for producing an air-cushion is also provided with two projections 10 located in the stern portion behind the keels 3, 4 and before the propellers 9 (FIGS. 1, 5) to protect the latter, said projections enveloping the bottom and a part of each side. The projections are formed by the plates 11 (FIG. 6) mounted at an acute angle to the bottom and sides. These plates are secured to the bottom and sides through the stiffeners 12. To protect the projections against damage during the mooring they are reinforced with beams 13.

The development of an air-cushion under the bottom of the craft occurs as follows:

When the craft moves at a service speed, the air supply unit forces air into the space formed by the plates 6 and the bottom 1 through the outlets of the ducts 7. The air consumption is rated so as to provide for formation of an air-cushion of a maximum length. If the craft moves and the air is not supplied into the above space, reduced-pressure zones are formed behind the steps 5. Thus, the air supplied to the steps 5 spreads over the width of the bottom. The air-cushions are increased to the largest length for the given speed of the craft.

When the craft reaches its service speed, the length of each air-cushion becomes equal to the distance 1 between the steps as shown in FIG. 7.

If the air is supplied to the foremost or bow step 5, the aircushions behind the other steps are formed by theair carried away by the flow of water from the air-cushion behind the first step.

The projections protect the propellers of the propelled craft against penetration of air from the air-v for producing 'air-cushionsf said outlets being positioned between said keels; steps forforming the air-cushions rar-, ranged between said keels on the bottom and spaced from one another at a distance determined by the formula I kl",

where Vis a service speed of the craft, k is a coefficient vary,- ing within the range of 0.2 to0.4,,said outlets being located adjacent at least the foremost of said steps, each step being a plate mounted at an acute angle to the bottom and I overlapping'the adjacent outlets and forming with the bottom a space supplied with air.

2. A craft as claimed in claim 1 comprising sides and a stem portion and at least one projection enveloping the bottom and a a portion of each said side. I

V I t t I i 

1. A craft comprising a bottom in the form of a continuous profile, keels extending along said bottom, air ducts having outlets arranged in said bottom through which air is supplied for producing air-cushions; said outlets being positioned between said keels; steps for forming the air-cushions arranged between said keels on the bottom and spaced from one another at a distance determined by the formula l kV2, where V is a service speed of the craft, k is a coefficient varying within the range of 0.2 to 0.4, said outlets being located adjacent at least the foremost of said steps, each step being a plate mounted at an acute angle to the bottom and overlapping the adjacent outlets and forming with the bottom a space supplied with air.
 2. A craft as claimed in claim 1 comprising sides and a stern portion and at least one projection enveloping the bottom and a portion of each said side. 